The present invention relates generally to heart valves prostheses, and more particularly, to a heart valve prosthesis for use in humans with contacting surfaces to reduce wear.
Heart valve prostheses are known in the prior art. One of the most widely accepted form of a heart valve prosthesis is a hinged "leaflet" or occluder type heart valve. This type of heart valve includes an annular body member forming an annular passageway for the flow of blood and one or more hinged occluders that pivot to control the flow of blood through the passageway. In one configuration, two occluders are disposed in an opposed or a mirror image relation and are generally semi-circular in shape. In the closed position, each occluder covers half of the passageway. Each occluder includes integrally formed rounded ears that extend outwardly from short straight sections of the perimeter edge. The ears are received within recesses which are formed in an inner surface of the annular body member. In one configuration, the recesses have been formed having surfaces of at least partial revolution of circular or nearly circular arcuate surfaces. Each ear is formed having a selected radius. The corresponding recess is formed having a slightly greater radius. When each occluder is disposed within the corresponding recess of the annular body member, a corresponding pivot axis is formed between each of the ears for each occluder.
The occluders pivot to open and close the passageway. When the heart undergoes contraction or systole, the occluders pivot from the closed position to the open position and allow blood to flow through the passageway. When contraction of the heart is complete and blood tends to flow back through the passageway in the opposite direction, the occluders close to maintain pressure. The recesses are formed with stop surfaces that are generally perpendicular to portions of the inner surface adjacent each recess. Planar surfaces of the ears engage the stop surfaces to limit opening and closing of each occluder and pivot against apex surfaces formed between the stop surfaces when the occluders move between the open and closed positions.
Durability and reliability of heart valves prostheses are of utmost concern. In view that each occluder will open and close approximately 38 million times during the course of a year, contact between moving parts gives rise to wear. While perhaps minimal by some standards, any reduction of wear between parts is always desired.
U.S. Pat. No. 4,689,046 describes a heart valve prosthesis having occluder ears formed as conic section surfaces, which are truncated in perpendicular planes. A pair of ear seating recesses are formed within an inner annular surface. Each recess includes a flat end wall or end face surface, a pair of opposed, truncated frustoconical or bevelled side wall surfaces, and horizontally extending rounded ear support or seating surfaces.
As described above, it is well known that the ears of the occluder pivot over the apex surfaces between the open position and the closed position. In U.S. Pat. No. 4,689,046, the apex is rounded so that when the occluder moves from the open position to the closed position, or from the closed position back to the open position, the surface of the ear rolls against the apex surfaces. As stated in the patent, this construction distributes the area of contact upon the ear surface, allowing a floating action, which extends wear.